Springs and spring suspensions are widely known. In automotive vehicles, leaf springs comprising, as a rule, a plurality of resilient metal strips have gained the widest application. The main disadvantage of the leaf springs is that they constitute from 8 to 10% of the total mass of motor vehicles. Moreover, in order to absorb shocks caused by heavy loads, the number of strips in the spring must be increased, thereby affecting the damping capacity of the spring.
The progressive-rate springs possess the best damping capacity. For example, known in the art is a spring comprising a resilient strip provided with bent ends pivotally connected with a supporting structure (see German Pat. No. 543,638 published 8 Feb. 1932). However, to permit damping of large dynamic loads by means of such a spring, it is necessary to use a plurality of resilient strips in contact therebetween, each of which (similar to other prior art leaf springs) is capable of bending in the plane of its lowest rigidity, a plane which coincides with the plane of action of an external load. This spring is also characterized by a complex design, which is due to the necessity of using mounting members to ensure load induced contact between flat and bent strips. To gain load induced interaction between the above-described spring and the vehicle components joined therewith it is necessary to provide at least three devices, namely two supporting assemblies disposed at the spring ends and one assembly disposed at the middle portion to take up external loads.
Also known in the art is a flat U-shaped spring operating as a girder freely lying on two supports (see D. D. Churabo, Detali i uzly priborov, Moscow, "Mashinostroenie", 1965, p. 368, FIG. 24, 3a). This spring is also capable of bending under the action of external forces in the plane of its lowest rigidity, i.e. it can not withstand considerable loads (in the order of hundreds of kilograms forces) until an adequate increase in the thickness thereof, such an increase nevertheless leads to a decrease in the damping capacity and to an increase in the spring mass. To render such a spring operative at least three devices for load induced interaction with the vehicle components are to be provided, namely two supporting means at the leg portions, and one means disposed in the middle portion to take up external loads. Such springs have not found wide application in vehicle suspensions.
A spring is generally used as a resilient means of vehicle suspensions. A spring suspension may comprise a guiding means, and a damping means (damper).
Suspensions provided with leaf springs are bulky while those provided with coil springs are complicated. For example, the suspension disclosed in USSR Inventor's Certificate No. 87580, comprises road coil springs disposed within a housing which is fixed to the sprung portion of a vehicle, and guiding double-arm levers (two levers per wheel). Long arms of the levers are pivotally joined with a wheel axle of the vehicle. The fulcrum of each lever is also pivotally connected to the sprung portion of the vehicle while the short arm interacts with the above-mentioned springs.
The above-described suspension provides for a substantially rectilinear up and down movement of the wheels when crossing an obstacle, though it is also characterized by a complex design and significant mass. The complexity of such a suspension is due to the fact that resilient and guiding devices of each wheel are disposed within a separate housing mounted outside the frame of the vehicle and fixed to the frame either by means of a special girder structure (for front wheels), or by broad flanges (for rear wheels). Each of the housings contains two double-arm levers and three springs, two of which operate during the working stroke (when the wheel rises) and one spring provides a rebound effect (when the wheel goes down). Each of the springs is subjected only to compression. The heavy mass of the above-described suspension is due to the fact that parts utilized therein are subjected to considerable forces, concentrated forces among them. The parts must therefore be of large dimensions and heavy mass in order that the stresses arising therein lie within the safe limits. Thus, the short arm of the lever for the front wheels is subjected to a concentrated load which exceeds a force exerted on the long arm connected to the wheel axle by the ratio between the lengths of the short and the long arms, the ratio being 2.5 to 3.5. The above ratio cannot be decreased because the deflection of the road coil spring, determined by the required rigidity and dimensional limits thereof, is relatively low. The contact stresses arising in the elements of the higher kinematic and geometrically open pair between the short arm of the guiding lever, the spring plate being in contact over a rather small surface area, appear to be rather high, and in order to maintain the above stresses within allowable limits, it is necessary to increase the dimensions of the contacting elements thus resulting in a respective increase in the mass of the parts.
A more reliable articulation joint in this kinematic pair is impossible without further complicating the design.
Bearings of the double-arm guiding lever are loaded by the forces whose geometric sum affects the arms thereof. A substantial increase in the dimensions of the arms is required in view of the above ratio between their lengths, and which, in turn, results in an increase in the mass of the housing containing the suspension.